1. Field of the Invention
The present invention relates to steering systems for aircraft landing gear, and more particularly to steering systems for landing gear having bogie beams with multiple axles, such as landing gear with three axles and six wheels per bogie beam.
2. Description of Related Art
Landing gear for large aircraft have traditionally employed a telescoping shock-absorbing strut with a multi-wheel truck attached. U.S. Pat. No. 6,805,320 to Derrien et al. discloses a large aircraft landing gear structure having a bogie or rocker beam with three axles for at total of six wheels. A stated objective of such landing gear structure is to provide a connection structure suitable for effectively handling the twisting moments that are generated while the aircraft is turning during taxiing.
In order to assist in turning the aircraft, reduce side loads acting upon landing gear during turns, and reduce tire scrubbing, traditional main landing gears with six wheeled bogie beam configurations have required the aft axle to be steerable relative to the bogie beam. Most common approaches to provide for aft axle steering have utilized hydraulic actuators connected to directly or indirectly push or pull the aft axle to the desired steering angle.
Traditional push-pull steering systems must be sized to produce enough steering torque at the minimum moment arm within the steeling range. As a result, the available steering torque is higher than required for most of the steerable range.
Steering angle feedback in traditional landing gear steering systems is measured with an LVDT (linear variable differential transformer) mounted inside a steering actuator. When a push-pull steering actuator is mounted between a bogie beam and an axle and when the orientation of the LVDT axis is similar to that of the bogie beam axis, deflections in the bogie beam itself are recorded as LVDT movement, resulting in false steering movement signals.
Such conventional methods and systems have generally been considered satisfactory for their intended purpose. However, there is still a need in the art for a landing gear steering system that allows for improved size and weight compared to traditional push-pull steering systems, while still meeting axle torque requirements. There also remains a need in the art for such steering systems that provide improved steering angle feedback. The present invention provides a solution for these problems.